Solvent extraction process



0ct.24,1944.- 7' R Q Mms EAL 2,360,860

SOLVENT EXTRACTION PROCESS Filed Feb. 8 1943 Raf'finaTe m fiowenil' 8 Recovery \nvznfors'. Rupzr f C. Morris Edward C. fihoml Patented Oct. 24, 1944 SOLVENT EXTRACTION PROCESS Rupert C. Morris, Berkeley, and Edward C.

Shokal, Oakland, Calif., assignors to Shell Development Company, San Francisco, Calif., a corporation of Delaware Application February 8, 1943, Serial No. 475,210

11 Claims.

This invention relates to a process for separating mixtures of fatty acids or fatty acid esters by extraction with selective solvents comprising a sulfolane.

The compound sulfolane has the formula:

Its derivatives are compounds wherein one or more of the hydrogen atoms is replaced by an organic radical which may contain a polar grouping and more specifically may contain oxygen, nitrogen, sulfur and/or halide atoms. In hydrocarbon-substituted sulfolanes the hydrocarbon radicals are preferably alkyl radicals. sulfolane derivatives containing oxygen include hydroxy sulfolanes, sulfolanyl ethers, and esters; sulfolane derivatives containing nitrogen include sulfolanyl amines, nitriles and nitro sulfolanes; sulfolane derivativescontaining sulfur include sulfolanyl sulfides, sulfox des and sulfones. Other sulfolane derivatives may contain halide radicals, inorganic ester or mixed radicals of those above mentioned, such as acid amides, halohydrins, sulfonamides, etc. Derivatives may be made by condensing a conjugated diolefin with sulfur dioxide, and then subjecting the resultant product to hydrogenation, alkylation, hydration, amination, chlorination, nitration and/or other substitution or addition reactions.

It is a purpose of this invention to separate mixtures of fatty acids and fatty acid esters into various fractions economically, efilciently and effectively by solvent extraction. Some specific purposes, among others, are to produce various fractions of fatty acids and fatty acid esters,

particularly suitable for use in paints, synthetic resins, food products, plastics, soaps, etc.; to produce pure fatty acids and fatty acid esters; to separate mixtures of fatty acids and fatty acid esters of different degrees or types of unsaturation into fractions containing a higher ratio of the more unsaturated or more actively unsaturated components than the original mixture; and to provide a method of extracting fatty oils from pulpsor meals containing them and leaving most of the phosphatides in a readily removable form in the meal.

Generally, the process of this invention comprises the steps of (A) contacting the mixture to be separated in the liquid state with .a liquid selective solvent to produce a rafflnate phase and an extract phase, (B) separating the two phases from each other, and (C) removing the solvent carried out in any suitable manner known from at least one of said phases to produce a raffinate and/or an extract and, usually, also recovering the solvent removed for further contact with more of said mixture. These steps, common to all solvent extraction processes, may be to those skilled in the art.

The accompanying drawing is a general flow diagram of a solvent extraction process.

A mixture to be separated is introduced in the liquid state through feed line I into contact zone 2 and admixed with a suitable sulfolane introduced into the same zone through a separate line 3. This is the first step (A) in all solvent extraction processes. Suitable equipment for carrying it out may comprise either an impinging jet mixer, an agitation vessel, a baffle plate column, or a packed tower.

In the contacting zone the mixture and sulolane are caused to produce a raflinate phase and an extract phase which are separately withdrawn respectively through lines 6 and 5. If separation of phases has not occurred under the conditions employed, cooling or injection of a demixing agent, etc., may have to be employed. This is the second step (B) of all solvent extraction processes, namely the separation of two phases produced in the contacting zone, and may be effected by settling, decantation, or centrifuging.

The third step (C) common to all solvent extraction processes comprises the recovery of sulfolane from one or both phases. The rafilnate phase is passed through line' 6 into the raflinate solvent recovery system 1 to produce a solventfree raflinate, which is withdrawn through line 8, and recovered sulfolane which is withdrawn through line 9 and is preferably returned through line 3 to contact zone 2. This recovry system may comprise a crystallization chamber, distillation column, or washing column. If the sulfolane is washed from the rafiinate phase an additional step for its recovery is necessary, such as distillation, to separate the sulfolane from the wash solvent.

' The extract phase is introduced into a solvent recovery system I0, which is similar to recovery system I. From recovery system H) a. solventfree extract is withdrawn through line It and the recovered sulfolane is withdrawn through line l2 and returned through line 3 to contact zone 2 for recontact with more of the mixture. Fresh sulfolane may be added to ,the'system from time to time through line I3 as required. v

The extraction temperature generally may range within wide limits, provided it is above the melting temperature of the solvent and below the boiling temperature of both the mixture and the solvent. The temperature for contacting the solvent mixture may be such that both the solvent and the mixture are completely miscible with each other and then the temperature may be lowered until phase separation takes place, or the contact may be entirely carried out below the temperature of complete miscibility of thesulfolane and the mixture. The extraction temperature may range between about 50 C, and about -|-,300 C.

The ratio of solvent to the feed mixture must be such that two phases will form. If the ratio is too high, all of the mixture may dissolve in the solvent; if it is too low, the solvent may dissolve in the mixture. Useful solvent-to-feed ratios may range from about /2 to 20 by volume.

Some specific examples of substances which may contain mixtures of fatty acids and/ or fatty acid esters include free fatty acids, fats, natural waxes, essential oils, and mixtures thereof. ,The fatty acids may be,derived by hydrolysis of the various fats listed below and may be saturated or unsaturated. Some specific examples of these fatty acids include capric, undecylic, undecylenic, lauric, sabinic, myristic, palmitic, palmitolinic, margaric, stearic, oleic, iso-oleic, linolenic, linoleic, stearoleic, ricinoleic, arachatic, behenic, brassidic, erucic, montanic, mellissic, psyllic, pysllostearic, etc.

The fats may be normally liquid or normally solid, drying, semi-drying, or non-drying, and animal or vegetable. Some specific examples of these fats are candlenut, hempseed, linseed, poppyseed, sunflower, tung, walnut, soya bean, beechnut, corn, cottonseed, pumpkin seed, rapeseed, mustard seed, almond, olive, peanut, hazelnut, and castor oils, palm oils. myristica oils, cocoanut butters, cocoanut oils, fish oils, liver oils, blubber oils, lard oil, sheeps-foot oil, neats-foot oil, animal fats, beef and mutton tallow, horse and beef marrow, butter, etc.

The waxes may be animal or vegetable in origin and may be normally liquid or normally solid, and saturated or unsaturated. Such waxes include sperm iooba oil, carnauba wax. montan wax, candelilla wax, cottonseed wax, palm wax, beeswax, insect wax, wool grease, psylla wax, etc.

Some essential oils comprising aliphatic esters are chamomile oil, geranium oil, heracleum oil, rose oil and fruit essences from such fruits as mirabelles, raspberries, peaches, red currants, apples, pears, strawberries, pineapples, bananas, quinces, etc. I

The sulfolanes of this invention may be employed as selective solvents by themselves singly or as mixtures of two or more, or as aqueous solutions. or together with auxiliary selective solvents or antisolvents, provided the additives to the sulfolane do not react with it and are stable under the temperature conditions of the process.

The sulfolane should not crystallize out of solution at the highest concentration which may occur at any point in the process and at a temperaity in such a kerosene frequently is an indication of poor selectivity.

Some suitable specific sulfolanes are: sulfolane,

hydrocarbon-substitutedsulfolanes such as alkyl sulfolanes preferably containing not more than about 14 carbon atoms; hydroxy sulfolanes such as 3-sulfolanol, 2-sufolanol, 3-methy1-4-sulfolanol, 3,4-sulfolanediol, etc.; sulfolanyl ethers such as methyl-3, propyl-3-, allyl-3-, butyl-3-, crotyl-3-, isobuty1-3-, etc.; methal1yl-3-, methyl vinyl carbinyl-3-, amyl-3, hexyl-3-, octyl-3-, nonyl-3-, glycerol alpha-gama-diallyl-beta-3-, tetrahydrofurfuryl-3-, 3,3,5 tetramethylcyclohexyl-3-, m-cresyl-3-=sulfolanyl ethers, corresponding 2-sulfolanyl ethers; disulfolanyl ethers, etc.; sulfolanyl esters such as B-sulfolanyl acetate, 3-sulfolanyl propionate, -butyrate, -caproate, etc.; N-sulfolanes such as 3-sulfolanylamine, N- methyl, N-ethyl, N-N-dimethyl, N-allyl, N-butyl, N-octyl-3-sulfolanylamines, etc.; sulfolanyl sulfides such as ethyl-3-, tertiary butyl-3-, isobutyl- 3-, methallyl-3-sulfolanyl sulfides, di-3-sulfolanyl sulfide, etc.; sulfolanyl sulfones such'as methyl-3-, ethyl-3-, propyl-3-, amyl-3-sulfolanyl sulfones; sulfolanyl halides such as 3-chloro-, 3,4-dichloro-, 3-chloro-4-methyl sulfolanes, etc.; and mixed sulfolanes such as 4-chloro-3-sulfolanol, 4-chloro-3-sulfolanol acetate, 3-sulfolanyl amine hydrochloride, N(3-sulfolanyl) acetamide, etc.

Of the sulfolanes useful in this invention, some are more heat-stable than others; thus, in particular, the halogen, amine, acid, some aldehyde, and some ester derivatives are relatively heatunstable. Some may begin to decompose at temperatures as low as 150 C. Other sulfolanes, on the other hand, are extremely heat-stable even at temperatures as high as 300 C.

Some commonly known solvents, selective solvents, and/ or modifying agents which may be employed in conjunction with the sulfolanes include water, various monoand poly-hydric alcohols such as methanol, ethanol, propanol, furfuryl alcohol, benzyl alcohol, glycols, glycerols', etc.;

various ketones such as acetone, methyl ethyl ketone, diethyl ketone, cyclopentanone, benzophenone, phenyl tolyl ketone, diphenylene ketone, etc.; various aldehydes such as crotonaldehyde, acrolein, furfural, etc.; ethers such as ethylene glycol and diethylene glycol mono-alkyl ethers, monoand diglycerol ethers, glycerol diethers, chlorinated dialkyl ethers (e. g. beta-beta-dichlorethyl ether), dioxane, etc.; lower aliphatic acids such as formic, acetic, propionic acids, acetic anhydride, etc.; esters such as benzoic, phthalic acid esters, etc.; phenol, cresylic acids, alkyl phenol mixtures, naphthols, alkyl naphthols, etc.; liquid ammonia, various organic amines such as lower aliphatic primary amines having one to eight carbon atoms, aniline, alkyl anilines, morpholine, diphenyl amine, ditolylamine, etc.; various nitriles such as acetonitrile, propionitrile, lactonitrile, butyronitrile, benzonitrile, etc.; various nitro hydrocarbons such as nitromethane, nitroethane, nitrobenzene, nitrotoluene, nitroxyl enes, etc.; various pyridines and quinolines: liquid sulfur dioxide; various modifying salts such as those disclosed in U. S. Patent 2,246,257 to Kohn; and the like.

The sulfolane or mixture of sulfolane with auxiliary solvent must be at least partially and not more than partially miscible with the feed mixture to be separated under the conditions of the process.

Furthermore, antisolvents may be employed together with the sulfolanes such as are employed in the M0801 process for the countercurrent extraction of lubricating oils. Some such antisolvents include propane, butane. pentane, nhexane, iso-octane, paraillnic gasoline, kerosene. gas oil, lubricating oil, various ethers, trichlorethylene, carbon tetrachloride, etc. Still further, compounds of two or more solvents together with one. or more antisolvents may also be employed.

uid,was then allowed to cool toabout 25 C. at which temperature two phases were formed. The upper hydrocarbon phase was separated from the lower sulfolane phase and both were washed with hot water to remove the sulfolane, and then vacuum distilled to remove the octanes. About 50% of the original acids was contained in each phase. The extract and raflinate phases The amount of auxiliary or antisolvents which may be employed in conjunction with the sulfolanes to make up the solvent mayrange up to 90% by volume, preferably less than 50% by volume, of the solvent.

Example I A- sample of a mixture of fatty acids containing stearic, oleic and linoleic acids obtained from animal fats and having an iodine number of 52.2

(determined by the Wijs method-see Methods of Analysis of the Association of Oillcial Agricultural Chemistry," 4th 'ed., 1935, page 412), was contacted with unsubstituted fulfolane in the ratio of one part of the mixture to two parts of sulfolane. The mixture was warmed to approximately 80' C. at which temperature the mixture became one liquid phase. After mixing thoroughly the mixture was allowed to cool to about Example If A sample of a mixture of fatty acids containing a mixture of oleic and linoleic acids derived from animal fat and having an iodine number of 131.1 was contacted with unsubstituted sulfolane in a ratio of one part fatty'acid to one part sulfolane. The mixture was warmed to produce one liquid phase, thoroughly mixed, and then cooled to about 30 C., at which temperature two phases were formed. These phases were then separated and the sulfolane was removed from each phase by washing with water. of the original fatty acids was present in the extract were tested to have iodine numbers of 138.4 and 125.4 respectively, resulting in a difference in iodine number of 13.0.

We claim as our invention:

1. In a solvent extraction process for the separation of a liquid.mixture of compounds selected from the group consisting of fatty acids and fatty acid esters, the steps comprising contacting said mixture with a sulfolane which is liquid and stable at the temperature of contacting to produce an extract phase and a raflinate phase, and separating said phases.

2. The process of claim 1 wherein the mixture is an essential oil.

3. The process of claim 1 wherein the mixture is a fat.

4. The process of claim 1 wherein the mixture consists essentially of fats of different degrees of saturation.

5. The process of claim 1 wherein the mixture is a natural wax.

6. The process of claim 1 wherein the melting temperature of the sulfolane is below about 150 C.

7. The process of claim 1 whereinthe sulfolane at room temperature is less than by weight soluble in kerosene having a Watson characterization factor of at least 12.

8. In a solvent extraction process for separating a mixture of compounds selected from the group consisting of fatty acids and fatty acid esters, the steps comprising contacting said mixture with a' sulfolane which is liquid and stable at the temperature of contacting to produce an extract phase and a rafllnate phase, separating phase and the extract and rafnnate phases were separately tested to have an iodine number of 142.3 and 125.! respectively, resulting in a diflerence in iodine number of 16.6.

volumeof a sulfolane which is. liquid and stable at the temperature of contacting.

10. The process of claim 9 wherein the solvent I comprises more than 50% by volume of said sulcontaining oleic and linoleic acids obtained from octanes, was warmed to a temperature of about C. to produce a single liquid phase. The liqfolane.

11. The process of claim 9 wherein the solventto-mixture ratio ranges between $5 and 20 by volume.

RUPERT C. MORRIS. EDWARD C. SHOKAL. 

